As is generally known, structures for athletic games, such as baseball games and other athletic sports, are not provided with a roof so that athletic activities can be practiced in a natural environment. However, without a roof, athletic activities are obliged to be interrupted or to be called off if rain begins to fall during athletic activities or on a rainy day.
Recently, all-weather stadiums have been proposed and roofs, for example, a pneumatic film roof structure, for all-weather stadiums have become the object of attention.
However, the pneumatic film roof structure has the following disadvantages.
First, when an athletic stadium has a roof of a pneumatic film structure formed of films of a synthetic resin or the like, the athletic stadium is filled with pressurized air having a pressure slightly higher than the atmospheric pressure, and hence the athletic stadium needs to be sealed so that the pressurized air will not leak outside, which requires entrances and exits of a complicated construction for spectators and the like.
Secondly, such an athletic stadium makes internal lighting and ventilation difficult and spoils the enjoyment of practicing or watching athletic sports in a natural environment.